How are we able to speak, think, or perceive the world? What portion of our brain has such a large job to compute all this information? The answer is - the cerebral cortex portion of the brain, and it makes up for 85 percent of your brain weight! Let's explore why it is so important both in size and function.
- What is the cerebral cortex?
- What are the functional regions of the cerebral cortex?
- What are motor functions of the cerebral cortex?
- What are sensory functions of the cerebral cortex?
The Cerebral Cortex: Explanation
Within our brain are several different systems that allow for the multitude of functions that our brain is capable of. One of these important components is the cerebral cortex. The cerebral cortex has a thin layer of a fabric-like area of the brain consisting of numerous interconnected neural cells. The purpose of the cerebral cortex is to process the massive amount of information that bombards our senses constantly.
Functional Regions of the Cerebral Cortex
Let's take a moment to understand the structure of the cerebral cortex and how it is composed. If we open the skull to take a look, our first impression may be that we see a wrinkly walnut-like mass inside. The cerebral cortex is in charge of up to 23 billion nerve cells and 300 trillion synaptic connections (Myers, 2014). Speaking to these neuron cells are the glial cells. Their primary focus is to protect and communicate with other cells. Also, they have an important role in our ability to learn and think.
Walnut brain, flaticon.com.
Each hemisphere's cortex has four lobes divided by fissures (or folds). These four lobes are the frontal, parietal, occipital, and temporal. What does each one do?
Cerebral Cortex Lobes |
Frontal lobes - making plans and judgments, speaking, and muscle movements. |
Temporal lobes - receive information from the opposite ear. |
Parietal lobes - receive information from touch. |
Occipital lobes - receive information from our visual fields. |
Also, another part of the cerebral cortex concerned with the sense of smell is the so-called olfactory cortex.
Motor Functions of the Cerebral Cortex
In 1870, German physicians Gustav Fritsch and Eduard Hitzig decided to zap a few places in the brain to see what would happen. They discovered that when they sent an electric stimulus to the back of the frontal lobe, it created an involuntary movement. There was also the realization that when the right side of the cortex was stimulated, it would create movement on the left side of the body, and the same was for the opposite. This was the discovery of the motor cortex.
Motor cortex functioning. wikimedia commons.
Motor Cortex
Once there was an understanding that a brain does not have sensory receptors, this opened up the possibility of much more discovery. Otfrid Foerster and Wilder Penfield used this to their advantage and began creating experiments that would help map out the motor cortex. Foerster and Penfield were able to stimulate portions of the motor cortex, which allowed them to learn that each motor cortex area had a specific job. For example, when stimulated, particular areas could create movement in the thumb. There was also a new understanding that the motor cortex sends messages outwardly in response to stimuli.
Brain-Computer Interfaces
Learning this plethora of information has opened doors to multitudes of possible further research that could help patients who have suffered strokes or have had other types of damage to the cortex. With the creation of brain-computer interfaces, researchers can now match brain signals. What does this mean?
Brain-computer interfaces, flaticon.com
Now, it is possible to create neural prosthetics for patients who have had severe neural damage. Now, a stroke survivor can use brain-computer interfaces to move a robotic hand or robotic arms. The first such case was a 25-year-old man implanted with a tiny microchip in his cortex. This allowed him to play video games or even draw shapes on a corresponding computer screen (Myers, 2014).
Functions of the Cerebral Cortex Lobes
Let's dive deeper into other aspects of the functioning of the cerebral cortex
Association Areas
All the other cortex areas that were not mentioned are still essential and used for our daily brain activity. The difference here is that these larger areas, if stimulated, would not result in an outward response. These larger areas of the brain are busy with higher thinking and functions. We call these the association areas of the brain, and they are located in all four lobes. Because of this large area, it is not easily mapped in comparison to the cortexes, such as the auditory cortex and the somatosensory cortex.
Although the association areas are not mapped or organized as well as other areas, their importance is just as vital. If there is damage, like most brain areas, the effects (biologically and psychologically) can be detrimental to a person. A great example of this is the very known story of Phineas Gage.
Phineas Gage
In the case of Phineas Gage, there was significant damage to his prefrontal cortex. Phineas had a terrible accident resulting in an iron rod through his left cheek and out of the top of his skull. If damaged, the prefrontal cortex can change a person's personality and remove inhibitions, which just so happened to be the area that was damaged for Phineas. While he could sit right back up and healed seemingly well, there was a very obvious change. It was reported that his behavior became irritable and profane. His memories and functions seemed untouched. However, his personality had changed entirely. Since then, there have been other accounts of the same changes in personality for those who have had a damaged prefrontal cortex.
This example is one of many that show the absolute necessity of association areas. While not neatly organized into tiny brain areas, association areas all have higher functioning jobs within our brains.
Sensory Functions of the Cerebral Cortex
A motor cortex sends messages outwardly. Guess what part receives messages? The somatosensory cortex portion of the cerebral cortex. Penfield also understood that this cortex area was in charge of receiving information from skin senses and movement of body parts. This area was named the somatosensory cortex.
Somatosensory Cortex
Penfield realized that when he stimulated certain areas of the somatosensory cortex, the person reported feeling as though someone or something was touching them (for example, on their cheek). He also learned that if the area being stimulated is hyper-sensitive, which means that a larger portion of the somatosensory cortex is devoted to it. A common example is a super-sensitive area, the lips. The lips are very sensitive in comparison to our thumbs.
Touch is not the only stimulation that sends messages to our cerebral cortex. For example, our auditory cortex is the brain area that allows us to receive information in the form of sounds. Sounds traveling to your ears are processed by the opposite side of your auditory cortex (the left ear hears the sound. Therefore, the right auditory cortex is the area it is processed).
Functions of the Cerebral Cortex - Key takeaways
- The cerebral cortex has a thin layer of a fabric-like area of the brain consisting of numerous interconnected neural cells.
- The purpose of the cerebral cortex is to process the mass amount of information that bombards our senses constantly.
- Speaking to these neuron cells are the glial cells. Their primary focus is to protect and communicate with other cells. They also have an important role in our ability to learn and think.
- Each hemisphere's cortex has four lobes divided by fissures (or folds).
- Frontal lobe - making plans and judgments, speaking, and muscle movements.
- Temporal lobes - receive information from the opposite ear.
- Parietal lobes - receive information from touch.
- Occipital lobes - receive information from our visual fields.
References
- Myers, D. G. (2014). Myers’ Psychology for AP (Second ed.). Worth Publishers.
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